PURPOSE: The purpose of this systematic review was to investigate the quality and outcome of studies into maxillary anterior tooth proportion and to determine whether dental proportion ratios based on different geographic regions are appropriate.
MATERIAL AND METHODS: An electronic search was conducted using PubMed, MEDLINE, Google Scholar, Embase, Scopus, Cochrane Library, Web of Science, and Science Direct databases. English-language articles reporting with the specific combination of medical subject heading (MeSH) key words were analyzed by 2 investigators. The titles, full text, and abstracts were scanned by investigators independently to identify articles that fulfilled the inclusion criteria. The general characteristics, outcomes, and quality of each study were reviewed and analyzed systematically.
RESULTS: The search plan resulted in a total of 73 articles until September 2020; of which, 16 articles fulfilling the inclusion criteria were selected. The geographic distribution of the selected article revealed 12 articles from Asia, 2 from Continental Europe, and 2 from the United Kingdom. Golden percentage values of 25%, 15%, and 10% for central, lateral incisor, and canine teeth were not found. The mean predicted dental percentage was either larger or smaller than the successive widths of maxillary natural anterior teeth.
CONCLUSIONS: The golden percentage could not be used to formulate a smile design. Rather, the dental ratios should be set on a racial and ethnic basis for a population.
PURPOSE: The purpose of this systematic review was to examine the existing evidence on dental proportion to evaluate the existence of RED proportions in the esthetic smile in different geographic regions.
MATERIAL AND METHODS: A systematic search was conducted by reviewing different databases. The focused question was "Does RED proportion exist in esthetically pleasing smiles in different populations around the world?" The search included articles with a combination of MeSH keywords based on dental proportion from January 2000 to July 2020. The titles and abstracts were identified by using a search protocol. Full text of the articles was independently evaluated. The systematic review was modified to summarize the relevant data. The general characteristics, outcomes, and quality of studies were reviewed and analyzed systematically.
RESULTS: Seventeen studies were selected from the reviewed articles. Three studies were conducted in Europe, 10 in South Asia, and 4 in Western Asia. Eleven studies found that the mean perceived ratio of anterior teeth was not constant when progressing distally. Five studies reported that the ratio was constant in a small percentage of their populations, and 1 suggested that the ratio was constant if it remains between 60% and 80%. The central-to-LI and Ca-to-LI proportion values were not constant. Overall, the Ca-to-LI proportion values were higher than the central-to-LI proportions.
CONCLUSIONS: RED proportions were not found in the successive widths of maxillary anterior teeth among the reviewed data from different geographic regions. RED proportions are not the only standard for restoring esthetic smiles worldwide, and anterior tooth proportions differ among populations based on their race and ethnicity.
METHODS AND FINDINGS: We searched the major electronic databases Medline, Embase, and Google Scholar (January 1990-October 2018) without language restrictions. We included cohort studies on term pregnancies that provided estimates of stillbirths or neonatal deaths by gestation week. We estimated the additional weekly risk of stillbirth in term pregnancies that continued versus delivered at various gestational ages. We compared week-specific neonatal mortality rates by gestational age at delivery. We used mixed-effects logistic regression models with random intercepts, and computed risk ratios (RRs), odds ratios (ORs), and 95% confidence intervals (CIs). Thirteen studies (15 million pregnancies, 17,830 stillbirths) were included. All studies were from high-income countries. Four studies provided the risks of stillbirth in mothers of White and Black race, 2 in mothers of White and Asian race, 5 in mothers of White race only, and 2 in mothers of Black race only. The prospective risk of stillbirth increased with gestational age from 0.11 per 1,000 pregnancies at 37 weeks (95% CI 0.07 to 0.15) to 3.18 per 1,000 at 42 weeks (95% CI 1.84 to 4.35). Neonatal mortality increased when pregnancies continued beyond 41 weeks; the risk increased significantly for deliveries at 42 versus 41 weeks gestation (RR 1.87, 95% CI 1.07 to 2.86, p = 0.012). One additional stillbirth occurred for every 1,449 (95% CI 1,237 to 1,747) pregnancies that advanced from 40 to 41 weeks. Limitations include variations in the definition of low-risk pregnancy, the wide time span of the studies, the use of registry-based data, and potential confounders affecting the outcome.
CONCLUSIONS: Our findings suggest there is a significant additional risk of stillbirth, with no corresponding reduction in neonatal mortality, when term pregnancies continue to 41 weeks compared to delivery at 40 weeks.
SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42015013785.